Periscope lets users easily stream footage from their devices to their followers. Viewers can comment and send "hearts" to the streamer. The footage can be then replayed later — a key difference to Meerkat, where the footage is gone for good once the stream is over.

A large part of Twitter's appeal is its popularity with celebrities, and it looks like the company's hoping this star power can provide a similar draw to Periscope. "Breaking Bad" actor Aaron Paul, astronaut Chris Hadfield, magician David Blaine, high-profile businessman Mark Cuban and skateboarder Tony Hawk are among those already using the platform.

Periscope videos aren't integrated directly into Twitter — you have to install the separate app. Greater integration may come later, however. Twitter also owns Vine, a 6-second video app, and the clips can be embedded directly into users' Twitter timelines and viewed without leaving the main app.